Multi-Input Multi-output (MIMO) technique may implement space division multiplexing by adopting a multi-stream transmission technique to improve data transmission rate when the quality of a channel is relatively good, and acquire a diversity gain by adopting a single-stream transmission technique to improve date transmission reliability when the quality of a channel is relatively poor.
An effective combination of Automatic Repeat Request (ARQ) and Forward Error Correction (FEC) provides not only a higher reliability than the reliability of a single FEC system but also a higher system throughput than the throughput of a single ARQ system. Therefore, with a strong need for a high-data-rate service or a high-reliability service, Hybrid Automatic Repeat Request (HARQ) already becomes a key technique in wireless communications and is studied in depth.
The MIMO technique and HARQ technique are already applied in the field of wireless communications, for example, they are applied both in a Worldwide Interoperability for Microwave Access (WiMAX) system and a Long Term Evolution (LTE) system. But in a multi-antenna system, Antenna Gain Imbalance (AGI) may reduce radiation power and affect the performance of a receiver, thus it is desired to study AGI's effect on the performance of system and to change a transmission strategy and a retransmission strategy, so as to optimize the performance in the presence of the AGI.